Work feeding and holding mechanism for machine tools



March 27, 1951 G. F. JOHNSON WORK FEEDING AND HoLDING MECHANISM FOR MACHINE TOOLS 6 Sheets-Sheet l Filed Feb. 3, 1948 Zmventor GAY/e? e/vofyso? Gttornegs March 27, 1951 G. F. JOHNSON WORK FEEDING AND HOLDING MECHANISM FOR MACHINE TOOLS 6 Sheets-Sheet 2 Filed Feb. 3, 1948 Snventor Gornegs March 27, 195.1- G. F; JoHNsoN woRK FEEDING AND HOLDING MEcHANIsM Fon MACHINE TooLs 6 Sheets-Sheet 5 Filedv Feb. 3, 1948 March 27, 1951 G. F. JOHNSON WORK FEEDING AND HOLDING MECHANISM FOR MACHINE TOOLS e sheets-sheet 4 Filed Feb. 3, 1948 Gttomegs G. F. JOHNSON WORK FEEDING AND HOLDING MECHANISM FOR MACHINE TOOLS March 27, 1951 Filed Feb. 3, 1948 G Sheets-Sheet 5 March 27 i953 1 G. F. JOHNS f WORK FEEDING AND HOLDUNMEOHANISM 295469752 FOR MACHINE TOOLS Filed Feb. 5, 1948 6 Sheets-Sheet 6 @www 5N QNNN RN RN J1 l iwww NNN hmm L] n mmm ON mmm mw www QN Rw .S m uw ma oww QN su E SQ n@ NNN @u @Q SN A QON `N NON W`m .www mom E am QN Sw N m NSNEN mem. N w@ QON #ON mwN GN EN J N Y Q Patented Mar. 27, 1951 WORK FEDIN G AND HOLDING MECHASM FOR MACHINE TOOLS Gien F. J o hnsn, Detroit, Mich., assignor t0 Bower Roller Bearing Company, Detroit, Mich., a corporation of Michigan Application February 3, 1948, Serial No. 6,086

12 Claims. 1

This invention relates to grinding machines, and in particular to feeding and chucking mechanisms for centerless grinding machines.

One object of this invention is to provide an automatic feeding and chucking mechanism for feeding and holding work pieces in a centerless grinding machine, whereby the work piece, such as an anti-friction roller-bearing cone, is carried automatically through a sequence of feeding, chucking, grinding and unchucking operations which are synchronized with the operation of the grinding machine as a whole.

Another object is to provide an automatic feeding and chucking mechanism for externally grinding conical work pieces in a centerless grinder wherein the workpieces are fed automatically from a chute to a chuck which grasps them one by one long enough to subject them to the grinding operation, after which the chuck automatically releases the workpiece, whereupon the feeding device lifts the workpiece upward and deposits it in a delivery chute Another object is to provide an automatic feeding and chucking mechanism of the foregoing type for centerless grinding machines wherein -the chucking mechanism contains automatically protracted andV retracted fingers which are timed to synchronize with the operation of the grinder and feeding device in such a manner that they are retracted completely while the feeding device is depositing a workpiece in the chucking area, after which the chucking fingers are automatically protracted and brought into engagement with the workpieceso as' to push it firmly against an abutment while the grinding operation is carried out, the fingers" being then retracted to release the workpiece while a portion of the feeding device lifts it upward to a delivery chute.

Another object is to provide an automatic feeding and chucking mechanism of the fore-- going type wherein the workpiece feeding device includes a vertically movable plunger which is engageable with a feed regulating arm succes'- sively into feed permitting' and feed ypreventing positions, thereby regulating the delivery of workpieces to the chuck in timed relationship with the operation of the other portions of the grinding machine.

Another object isv to provide an automatic feeding and chucking mechanism of the foregoing type' wherein the workpiece is approximately centered by workpiece supports and is urged by the chucking mechanism against a rotary driving member or back plate while it is being ground, the driving mechanism continuing to drive the workpiece as the latter is reduced in diameter by the grinding wheel while the chucking mechanism permits the workpiece to move downward slightly while stillurging it against the driving member, thus in effect floating while following the descent of the workpiece.

In the drawings:

Figure 1 is a top plan View of a centerless grinding machine equipped with an automatic feeding and chucking mechanism according to a preferred form of the present invention;

Figure 2 is a side elevation, partly in vertical section, of the tiltable grinding head and its associated mechanism shown in the upper righthand corner of Figure 1.

Figure 3 is a front elevation of the automatic feeding and chucking mechanism shown at the leftuhand side of Figure l, with the parts in their positions at the bottom of a feeding stroke;

Figure 4 is a horizontal section along the line 1 in Figure 3;

Figure 5 is a horizontal 5-5 in Figure 3;

Figure 6 is a horizontal section along the line 6-6 in Figure 3;

Figure 7 is a horizontal section along the line 'l-l in Figure 3; n

Figure 8 is a fragmentary vertical section along the lines 8-8 in Figures 4 and 9 Figure 9 is a side elevation of the automatic feeding and chucking mechanism shown in Fig'- ure 3 with the workpiece supplyand discharge chute omitted;

Figure 10 is a View of the central portion of Figure 9 partly in section adjacent the plunger rod;

Figure 11 is a fragmentary top plan view of the diaphragmeoperated valve and needle valve for controlling the pneumatic feeding motor shown in Figure 9;

Figure 12 is an approximately horizontal section along the slightly inclined line l2|2 in Figure 3 showing the workpiece lifter;

Figure 13 is a front elevation of the automatic feeding and chucking mechanism shown in Figure 3, with the parts in their positions at the top of the ejecting'stroke';

Figure 14 is an enlarged central vertical section through the workpiece chucking and rotating mechanism shown at the left-hand side of Figure 1 with the chucking lingers extending into their workpiece-engaging positions;

Figure 15 is a view similar to the right-hand portion of Figure 14, but showing the chucking fingers retracted into their tubular carrier prior to the withdrawal of the latter from the workpiece;

Figure 16 is a view similar to Figure 15, but showing the chucking finger carrier completely retracted and the workpiece completely ejected;

Figure 17 is a fragmentary .topy plan view of the tubular chucking finger carrier 'shown at the section along the line 4extreme right-handside of Figure 14;

Figure 18 is a front elevation of the chucking ringer carrier and lingers shown in Figure 11;

Figure 19 is a fragmentary vertical section along the line iiii9 in Figure i, showing the solenoidally operated valve for controlling the tilting of the grinding head shown in Figure 2 and at the right-hand side of Figure l;

Figure 20 is an enlarged fragmentary top plan view of the lower central portion of Figure 1, showing the grinding wheel engaging a conical workpiece held by the chucking device shown in Figures 14 to 18 inclusive;

Figure 21 is a fragmentary vertical section along the line 2i-2| in Figure 2; and

Figure 22 is a kdiagranrimatic cross-section through the Workpiece'being ground, showing the positions of the workpiece-locating and positioning members.

Grinding machine construction Referring to the drawings in detail, Figures l and 2 show a conventional type of centerless gri ding machine generally designated l to which the feeding and chucking mechanism, generally designated Il, is applied. The feeding and chucking mechanism il in turn consists generally of a feeding device l2 (Figures 3 to 13 inclusive) and a chucking device i3 (Figures v.li'to 1S inclusive). The grinding machine le is well known to those familiar with the centerless grinding technique and as its details form no part of the present invention, a brief description thereof will suflice.

The grinding machine lil is supported on a hollow base or bed i4 (Figures 1 and 2). Rising from the bed ifi and integral therewith are two spaced ears or bearing bosses l (one only being shown in Figure 2) bored to receive a pivot shaft ie which in turn passes through downwardly extending ears l1 forming a part of the housing i5 of the grinding head generally designated I9. r1`he housing 1B is approximately rectangular in horizontal outline (Figure l) and has spaced internal bosses 2d having aligned bores 2| and 22 in which a shaft 23 is journaled. The forward end of the shaft 23 is of reduced diameter as at 2@ and carries thereon a hub or collar 2E against which the beveled grinding wheel 26' is-clainped by means of a nut 21 on Athe threaded forward end 2S of the shaft 23. The threaded end 28 is further reduced in diameter from the portion 2d.

The grinding wheel 2?; (Figure 20) is provided with beveled portions 2Q and 3G which meet in a sharp peripheral'line or edge 3i. The width ofthe portion 28 corresponds to the width of the conical portion Si: of the workpiece W which, for purposes of illustration, is shown asrepresenting the inner race of a tapered roller bearing. The workpiece W, has the usual shoulders or flanges 33 and 34 separated from the conical portion 32 by annular grooves 35 and 35 respectively. The workpiece W (Figure is provided with the usual internal bore 31 by which it isl mounted on the shaft which it rotatably supports, in the machinery to which it is applied.

device I3 upon which the work- The chucking is described piece W is mounted and rotated below in detail.

The rearward end of the shaft 23 is provided with a reduced diameter portion 3d to which is secured a pulley ES. The pulley 39 is driven by any suitable rotating means from a prime mover (not shown) such as a motor, thebelt fl@ being shown as one means of rotating the pulley 39.

In order to rock the grinding head I9 so as 'of a solenoid 18 from 'The timing device tion', is represented as consisting'of an accurately to swing the grinding wheel '25 into and out of engagement with the workpiece W, as for the purpose of inserting and removing workpieces W, the grinding head is provided with downwardly projecting spaced ears Lil (Figures 1 and 2) depending from the top wall d2 thereof. The ears 5l are bored to receive a pivot pin 43 which also passes through a block fifi connected to the upper end of a piston rod 5. The lower end of the piston rod E carries a piston head i5 which is reciprocaole in the bore di of a hydraulic cylinder 48.

The cylinder (i8 has upper and lower heads 4% and 56 respectively provided with bored and threaded bosses 5i and E32 into which are threaded pipes 53 and 55 respectively for conducting pressure uid such as oil to the cylinder Q8 and exhausting fluid therefrom. The upper head 4B is bored as at 55 for the passage of the piston rod 45 and counterbored as at 5E for receiving a packing 51. The latter is compressed by a tubular gland 5% through which the piston rod 45 also passes and which is threaded into the counterbore 5t and thus prevent leakage around the piston rod 45. The lower head 5e is provided with downwardly extending spaced ears ES (one only being shown in Figure 2) which are bored to receive a pivot shaft 60, the latter also passing through an upwardly extending ear 6l which is preferably integral with the base or ybed Id. Thus, by supplying pressure fluid to the pipe B, the piston head 36 and piston rod i5 may be moved upward to swing the head i9 around its pivot shaft I- and cause the grinding wheel 26 to swing into and out of contact with the workpiece W, as regulated by a cam-controlled stop mechanism (not shown) which is conventional and forms no part of the present invention.

The pipes 53 and 54 (Figure 1) are connected respectively to the bored bosses 62 and 63 at the opposite end ports of a conventional four- Way valve Bil which has acentral boredboss E5 containing the central port and having a pressure fluid supply pipe S threaded therein. The valve 6d is provided with ears or lugs 64a by which it is bolted to the bed or base I4. The valve 64 is also provided with a iiuid discharge pipe 61 (Figure 19) for the discharge of the fluid escaping from the opposite end of the cylinder i8 from that to which pressure fluidis admitted from the valve 84.

The four-Way valve 64 (Figure 1) is provided with the usual reciprocating valve rod 68 by which the valve is operated. The valve rod 68 is pivoted as at 69 to a link 10 which in turn is pivoted at 1l to an arm 12 (Figure 19) mounted on a vertical shaft 13. VAt its outer end the arm 12 is pivoted as at 14 to a link 15 which in turn is pivoted as at 16 to the armature 11 the winding of which av wire 19 runs to an electrical supply line 811 which is connected at the terminal 8| to an external source of electric current. A terminal 82 is connected to the opposite pole of the elec tric current source and is in turn connected to a line 83 containing a single-pole single-throw switch 84.

Running from the line 83 (Figure 1) is a wire 85 leading'to one terminal 86 of a ytiming device 81 of any suitable conventional type, from the opposite terminal S8 of which a wire 89 runs to the remaining terminal of the solenoid 18.

81, for purposes of illustrato compress the packing 51 Vof the. screw shaft timed rotating shaft 99 driven, for example, by an electrical synchronous motor (not shown). The shaft 99 carries a timing disc 9| with a peripheral projection 92 adapted to engage a similar projection 93 upon a spring arm 94. The latter carries a contact 95 adapted to engage a similar contact 99 upon an arm 91 when the arm Sii is pushed toward the arm 91 by the engagement of the projections 92 and 93 resulting from each revolution of the timing disc 9|. When this occurs, the circuit energizing the solenoid 18 from the electric current supply lines 99 and 83 is closed. This action pulls inward the armature 11 and with it the arm 12 and valve rod 68, shifting the valve 94 and reversing the direction of travel of the piston rod 45- and grinding head I9, as described below in connection with the operation of the invention.

The operation of the grinding machine I9 is controlled by the shaft 13 through conventional mechanism, either by a manually operated arm 99 or by a solenoidally shifted arm 99, both arms 99 and 99 being secured to the shaft 13. Pivoted as at |99 to the outer end of the arm 99 is a clevis |9| on a link |92. The link |92 at its opposite end carries a clevis |93 which is pivoted at |99 to a bell-crank |95 pivotally mounted as at |99 upon 4the bracket |91 bolted to the base or bed |11 (Figure 19). The opposite arm of the bell crank |95 is engaged by the upper end |98 of the upwardly moving armature |99 of a solenoid 9, the winding of which is in series with the current supply line 83.

Also in series with the line 83 is a normally open limit switch (Figures 1 and 2) which is bolted to the base or bed I4 and which has an operating plunger H2. The latter engages the spring arm 3 and forces its contact into engagement with a corresponding contact on a xed arm ||4 (Figure 2) to close the circuit in the line 83. The plunger ||2 is operated by an adjustable push rod ||5 which is slotted as at ||6 and bolted as at H1 to the housing' I3 of the grinding head I9. Thus, when the grinding head has moved backward and downward a suiilcient amount to engage the push rod ||5 with the switch plunger ||2, the latter closes the circuit in the line 83.

Also in series with the line 93 and located at the termination of the latter is a normally open feed limit switch ||8 (Figures 1, 8, 9 and 10) which is bolted to the feeding device |2, as described below. The limit switch ||9 (Figure 9) is provided with a xed arm i9 and a spring arm |29 operated by a plunger |2|. The line 33 is connected to the fixed arm ||9. A coil spring |22 urges the plunger |2| downward into its normally open position. Connected to the spring arm |29 is the end of the current supply line 89.

Checking mechanism Mounted on the base or bed I4 in an oblique direction are two guide rails |23 (Figure 1) of the dovetail type upon which a dovetail slide |24 is adjustably mounted. Journaled in the rearward end of the slide |24 is a screw shaft |25 which passes through the bridge portion |29 between the guide rails |23 and is provided with a squared end |21 for the application of a wrench or crank. The screw shaft |25 passes through a threaded bore |29 in the bridge portion |26 and isA locked in its adjusted position by lock nuts |29..on opposite sides thereof. The. inner end |25 is rotatably connected to the slide |24 on the under side thereof (not shown). By rotating the screw shaft |25, the slide |24 may be adjusted toward or away from the grinding wheel 25. The chucking device I3 ismounted upon a turntable |39 (Figure 1) which in turn is mounted upon a shaft |3| supported by the slide |29. An arcuate slot |32 and lock nut |33 threaded upon a stud |34 seated in the slide |24 serves to lock the turntable |39 in its desired position of inclination relative to the guide rails |23.

Mounted upon the turntable |39 above the strengthening ribs |35 (Figure 1) is a hollow elongated housing |39 having a hollow central portion |31 and end walls |38 and |39. The end walls 38 and |39 are provided with aligned bearing bores |99 and Idl respectively in which is journaled a tubular shaft |42 (Figure 14) having an enlarged hollow cylindrical head |43 on the forward end thereof. Keyed or otherwise drivingly secured as at |411 to the rearward end of the tubular shaft |42 is a gear |55. The latter meshes with an idler gear |96 (Figure 1) which is rotatably mounted upon a stub shaft |41, the forward end of which is journaled as at |49 in the housing extension 49 which extends laterally from the housing |35. Also journaled in the housing extension |49 is the armature shaft |59 of an electric motor |5| which is secured to the housing extension |49. The outer end of the armature shaft |59 carries a gear |52 which meshes with the idler gear |96. In this manner the tubular shaft |42 is rotated by the electric motor |5|.

An elongated cover member |53 serves to enclose the gears |45, |49 and |52. Bolted as at |54 (Figure 14) to the gear |95 is the inner end wall |55 of a cylinder |55 having a cylinder bore |51 closed at one end by a cylinder head |59 secured thereto as at |59. The side wall of the cylinder |59 and the cylinder head |59 are provided with connecting passageways |59 and |9| opening into the cylinder bore |51 adjacent the end wall |55. The opposite end of the passageway |9| communicates with an approximately U-shaped passageway |92 extending through a shaft |59 which is seated in a central bore in the cylinder head |58 co-axial with the axis of rotation of the cylinder |55 and tubular shaft |92. The shaft |94 on its inner end is provided with an enlarged head |63 and is held in position by a collar |99 threaded upon the shaft |64 adjacent the cylinder head |58. The shaft |69 is provided with a second longitudinal passageway |91 opening into the left-hand end of the cylinder |51.

In order to deliver compressed air or other pressure fluid either to the passageway |61 or to the connecting passageways |59, I9! and |52, the cylinder |56 is provided with a rotary air connection unit |68 (Figure 14) of which the hollow shaft |99 forms a part. The passageways |52 and |51 open into separate annular chambers |69 and |19 respectively formed in hollow annular casings |1| and |12 separated from one another by an annular member |13. The inner or forward end of the valve casing |1| is seated against a shoulder |14 formed by reducing the diameter of the shaft |64 immediately to the left of the collar |66.

The casings |1| and |12 are bored for the nassage of the reduced diameter portion. |15 of the shaft |54, the latter being provided with a still further reduced and threaded end portion |19 carrying a-.retaining nut |11 and washer |19. In this mannenthe casings |1| and |12 are-'held stationary while the shaft |64 revolves with the cylinder |56 and the tubular shaft |42. In order to seal the shaft |52 at the places where its reduced diameter portion |15 passes through the casings |1| and |12 and the annular member |13, each chamber |69 and |16 is provided with flanged annular sealing members |19 (Figure 14) which are spaced apart from one another at opposite ends of their respective chambers by cylindrical spacers |89 and |8| having peripheral ports |32 and |93 respectively. The ports |32 and |83 open into corresponding ports |96 and |85 in the casings |1| and |12, these ports being threaded to receive the ends of air pipes |35 and |81 respectively. The connections of the opposite ends of the pipes |36 and |31 will subsequently be described.

Reciprocably mounted in the bore |51 of the cylinder |59 is a piston head |88 which is secured as at |89 to the end of a rod |90. The rod |99 passes through a bore |9| in the end wall |55 and at its opposite end is provided with an internally threaded bore |92 into which is threaded the rearward end |93 of a shaft |94 which is locked in position by a nut |95. The shaft |94 passes through a bore |99 in the center of the tubular shaft |52 and its threaded forward end |91 is threaded into a bore |93 in a sleeve |99. The sleeve |99 is reciprocably mounted in a bore 296 formed in a flanged plate 29| which is bolted as at 292 to a anged plate 293, the latter in turn being bolted as at 294 to the hollow head |43. The flanged plate 26| is provided with axial grooves 265 which slidably receive elongated keys 206 secured by the screws 201 to the sleeve |99.

Also secured by the bolts 292 to the flanged plate 293 is a bell-shaped member 298 (Figure 14) the forward end portion of which is provided with an outer annular abutment surface 299 which serves as a back stop for the workpiece W. The forward end wall of the bell-shaped member 298 is also provided with an internal annular shoulder 219 which serves as a stop for a bar 2| l which is secured by a set screw 2 |2a in a transverse bore 2|2 in a plunger 2 I3 which is reciprccably mounted in a bore 2 I4 within the sleeve |99. The sleeve |99 in turn passes through a bore 2|5 in the bell-shaped member 298. A coil spring 2|5 constantly urges the plunger 2|3 and bar 2|| to the right, the bar 2| passing through elongated slots 251 in the sleeve |99.

The sleeve |99 at its forward or outer end (Figure 14) is provided with inwardly extending slots 2|8 (Figures 14, 1'7 and 18). The slots 213 are offset relatively to one another (Figure 18) and are provided with pockets or alcoves 2 9 (Figures 17). The pockets or alcoves 219 serve to receive the rounded ends 22|) of a pair of dogs 22| which are pivotally mounted in opposite directions upon a pivot pin 222 (Figures 14 to 18 inclusive). The dogs 22| are received within a slot 223 extending inward from the outer end of the plunger 213, the pivot pin 222 passing through the slot 223 (Figure 18) and being seated in aligned bores 229. The opposite ends 225 of the dogs 22| are in the form of contact fingers adapted to engage the forward edge of the workpiece W and push it rearwardly against the abutment surface 299.

Feeding mechanism The feeding mechanism i2 for feeding the workpieces W to the chucking mechanism i3 is mounted upon the latter and synchronized to operate with it. For this purpose, the housing |36 ariiacent the end wall |39 (Figure 14) is provided with a reduced diameter portion 226 which receives a bore 221 in an approximately hollow cylindrical housing extension 223. The forward end of the housing extension 22S is mounted upon an annular shoulder 239. The end plate 239 and housing extension 228 are secured to the housing end wall |39 by any suitable means such asbolts 23| and 232 (Figure 9). The end plate 239 is provided with an arcuate slot 233 (Figures 3, 13 and 14) concentric with the axis of the rotating sleeve |99, the end plate 239 having a bore 234 also concentric with the axis of rotation. The bell-shaped member 298 projects through the bore 234 into engagement with the workpiece W.

Mounted upon the end plate 239 in engagement with the forward face thereof are two angle blocks 235 and 233, each of which on its underside is provided with an arcuate rib 231 (Figure 14) which closely ts into the arcuate slot 233. The angle blocks 235 and 236 are bored to receive clamping bolts 235 which pass through the arcuate slot 233 and carry square nuts 239 on their threaded inner ends. Thus, the rotation of the bolts 238, such as by a screw driver, causes the angle block 235 or 236 to be either clamped tightly against the end plate 239 or released to slide in an arcuate path, guided by the engagement of its arcuate rib 231 with the arcuate slot 233. The angle blocks 235 and 236 are provided on their outer surfaces with shallow grooves 249 and 24| (Figure 13) which are directed generally toward the sleeve |99. Slidably mounted in the grooves 249 and 24| are stop bars 242 and 243 respectively, each being provided with an elongated slot 244 for adjustment relatively to a clamping screw 245. The inner end of the stop bar 242 is provided with a beveled straight end 246, whereas the stop bar 293 is provided with a beveled skew end 241, both being adapted to engage diiferent portions of the workpiece W (Figures 13 and 22). The stop bars 222 and 225 are preferably tipped with a hard wear-resisting material, such as tungsten-carbide. In order to ad just the stop bars 242 and 243 to and fro, each of the angle blocks 235 and 236 is provided with an adjusting screw 249 (Figure 13) which is threaded through the angle portion 249 of the block and which carries a look nut 259.

The top surface portion 25| of the housing extension 228 (Figure 14) is machined to receive the flanged base portion 252 of an upright or standard 253 (Figures 3, 9 and 13) which is secured thereto by the screws 254 (Figures 4 and 5). The standard 253 is provided with an elongated vertical guide portion 255 of approximately U- shaped cross-section and secured to the base portion 252 by the rib or web 256. The guide portion 255 of the standard 253 is provided with an elongated vertical guide groove 251 (Figure 4) in which a feed slide block 258 of T-shaped cross-section is reciprocably mounted. Retaining bars 259 are secured as at 259 to the guide portion 255 in order to hold the slide block 258 in assembly.

Secured to the slide block 258 as by the screws 26| isvthe upper supporting bar 292 of an approximately rectangular feed frame 263 (Figures 3 and 13) with a cross bar 264 from which parallel side members 265 and 265 extend downward and are interconnected at their lower ends by the inclined cross member 251 (Figure 12). Secured as by the screws 268 to the lower cross member 261 is a workpiece-supporting block 269 and in- 229 of an end plateY clined retaining member 210 which extends4 up- `--w.ard Asubstantially parallel to the inclined cross member 261. The side member 265 is provided with an elongated forwardly extending projection 21 I- which serves as a gate as it reciprocates vertically with the side member 265. Cooperating with the gate 21| is a supply chute 212 and a discharge chute 213 (Figure 3), the former holding a supply of unground workpieces W and the latter carrying away the ground workpieces. The chutes 212 and 2.13 are secured by the fasteners 214 and 215 respectively to the vertical arm of an angle bracket 216, the horizontal arm of which is secured by the fasteners 211 to the side of the housing extension 223 (Figure 9).

In order to guide the forward and rearward edges of the workpieces W, the feeding device I2 is provided with parallel guide plates 218 and 219 extending downwardly toward the grinding position of the workpiece W upon the workpiece holding sleeve |99. The outer or forward guide plate 218 has an integral U-shaped bracket 280 (Figure 5), the rearward arm of which is secured bythe fasteners 28| (Figure 10) to the standard 253. The inner guide plate 219, on the other hand, is secured by the fasteners 232 (Figures 3 and to the end plate 230 oi the housing extension 228. In order to retain the workpieces W in the supply chute 212 until it is desired to feed them to the feeding frame 263, an approximately L-shaped detent lever 283 is pivoted as at 28'4 (Figures 3 and 5) to the bracket` 280, whereas the outer end thereof is provided with a horizontal finger 235 which extends across the chute 212 and, in its lowered position (Figure 3), prevents the workpieces W from descending further downthe chute 212.

Pivoted as at 286 to an intermediate portion of thedetent lever 283 is a clevis 281 from which rises a plunger 283 encircled by a compression coil spring 289 (Figures 3 and 9). The plunger 288 near its upper end passes through a bore 290 in a bracket 29| extending outward from the standard 253. The upper end of the plunger 288 also passes' through a bore 292 in a forwardly projecting arm 293 and is adjustably held in position by a nut 294 threaded on the threaded upper end of the plunger 288. AS is subsequently explained in connection with the operation o the machine, the arm 293 is engaged by the upper cross member 264 of the eeding frame 233.when the latter nears the upper limit of its stroke, as shown in Figure 13, lifting the plunger 288 and swinging` .the detent arm 283 upward to move the linger 285 above the workpieces W and'into contact with the gate 21 I. v

As the slide block 258 reciprccates vertically in its guideway 251, it engages a contact arm 295 (Figures 3, 5, 9 and 10) pinned to a horizontal rod 296 which is journaled in a horizontal bore 291 (Figure 5)v in the standard 253. Pinned to the rearward end of the rod 233 is the hub of an arm V299 which is bored and threaded to receive an adjusting screw 299 which contacts the lower end of the switch operating plunger l2! of the limit switch IIB.

. The slide block 253 at itc upper end is provided. with a socket or 339 (Figure lil) into which the lcwei. end of a piston rod 30| is loosely received and is pivcted to the pivot pin 302 which extends to the slide block 258 and across the cavity 335i. The piston rod 39! passes upward. through a suitable bore 333 in the supporting plate 304 and thence into the cylinder bore 305 of a pneumatic cylinder 306 (Figure 9) Mounted onA the upper end ofthespiston rod'39I'is a piston i head 3 01 which reciprocates in the cylinder bore 305. rI Ilieupper end of the cylinder 393 is closed by an end cap 303 which has a boss 309 bored to receive the upper end of a pipe 3|0. The lower end ofH the cylinder 306 is encircled by a lower end member 3| I which is provided with a boss- 3 I 2, the 1atter`being bored to receive the upper end of a pipe 3|3 (Figure 9) The pipes 3|0 and 3|3 are secured at their lower ends to connections 3|4 and 3l5 of a compressed air valve 3|6 of a conventional type having a compressed air supply connection 3I1 to which is connected a compressed air supply pipe 3|8 (Figure 9). The valve 3 I6 is provided with an operating plunger 3|9 which is encircled by a coil spring 320 and has on its upper end a head 32| which passes through a exible diaphragm 322 and engages the' opposite sides thereof. The diaphragm 322 is secured by the fasteners 323 to a supporting ring 324 by way of a spacing ring 325 and a chamber casing member 323. The supporting ring 324 is in turn supported by a spider 321 (Figure 9) the hub of which is mounted on the upper end of the valve 3|6. The latter is mounted upon a hollow pedestal 323 which is secured as at 329 to the housing |36.

The chamber casing member 326 is cup-shaped so as to form a closed chamber 330 above the diaphragm 322, and has a boss 33| which is bored and threaded as at 332 to receive the vertical pipe 333 which leads to a T 334 (Figure ll). From the forwardend of the T 334 a pipe 335 leads to a needle' valve or bleed-ofi valve 335 having a needle valve member 331 which is screwed in or out relatively to the valve seat 333 by the hand wheel 339 mounted on the outer end ofthe' needlevalve member 331.` A pipe 349 is connected to the needle valve 336 on the opposite side thereof from the pipe 335.

From the opposite side'of the T 334, a compressed air supply pipe 34 leads to the outlet port of an air valve 342 (Figures l and 2) oi conventional construction and having avalve plunger 343 which is engaged by the lower end of an adjustment screw 344 threaded through one arm of a bell crank 345 and carrying a lock nut 346. The other arm of the bell crank 345 has a forked end carryhig the axle 341 of a contact roller 348. The bell crank 345 itself is pivotally mounted upon a pivot pin 349 which is mounted upon the upper end of a bracket 350 bolted as at 35| to the bed I4. The bracket 353 is provided with an arm 352 towhich the valve 342 is attached.

The roller 348 is so positioned as to be engaged by the beveled end 353 (Figure 2) of a swinging abutment arm 354 which is pivoted as at 355 to a block 356 (Figure 1) mounted on the side of the grinding head housing I3. The abutment arm 354 is urged upward against a stop pin 351 by a coil spring 353 connected at one end to the arm 354 and anchored at its opposite end to the grinding head I9. To the opposite side oi the valve 342 from the connection of the pipe 34|, a pipe 359 runs to a source of compressed air, such as a compressed air tank or pump. The compressed air supply pipe 359 is also connected to the branch pipe 3I3 which leads to the diaphragm-operated valve 3|6 (Figure 9) Another branch pipe 330 leads from the compressed air supply pipe 359 to the chucking control valve 33| (Figures l and 2). Thelatter is of a conventional type and is operated by a valve plunger or stem 362 which is pivotally connected as at 363 to a link 364 with an elongated slot 365. The link 364 is frictionally engaged by spaced friction washers 356 and 361 on opposite sides thereof (Figure 2l). The friction washers 366 and 361 are mounted on a stud 368 which at its rearward end is threaded into a bore 359 in the grinding head housing I8. A A spacing'collar 316 is arranged between the friction washer 361 and the housing I8 whereas the washer 366- is yieldingly urged against the link 364v and the latter against the washer 361 and collar 319 by a coil spring 31| which, at its opposite end, engages a washer 312 held imposition by a nut 313 mounted on the outer. end of the stud 368. By this arrangement, the housing I8 of the grinding head I9 can oscillate to and fro around its pivot shaft I6 (Figure 2) a much greater distance than is necessary to operate the plunger 362 of the valve 36|, the link 364 and washers 356, 361 slipping relatively to one another when the valve plunger 362 has reached the end f its stroke in either direction. The pipes |86 and |81 are connected to the chucking control valve 36| which, like the feed control valve 3|'6 (Figure 9) is mounted upon a hollow pedestal 314 secured as at 315 to the base or bed I4.

Operation In the drawings, except for Figures 13, 15 and 16, the parts are shown in the positions they occupy at the instantthe grinding operation is being concluded and the workpiece W is ready to be unchucked and transferred to the discharge chute. while an unground workpiece is waiting to be fed to the chuck. For purposes Y of illustration, the workpieces W are shown (Figures 14 and 20) to be the internal cones or conical races of tapered roller bearings.- These require high precision grinding on their conical surfaces von which the tapered rollers roll,.."and such grinding is performed by the machine equipped with the chucking and feeding devices of the present invention. Let it also be assumed that a supply of unground workpieces W-has been placed in the upper or feed chute 212 (Figure 3) and that the pipe 359 has been connected to a source of compressed air.

Let it further be assumed that the electric. wires 8|), 83, 19 and 85 have been energized (Figure l) by connecting their terminals 8| and 82 toa source of electricity. Let it also be assumed that the motor II has been energized so as to rotate the hollow shaft |42 which drives the chucking unit I3 and that the pulley 39 is being driven so as to rotate the grinding wheel shaft 23 and grinding wheel 26. Prior to the commencement of the grinding operations, it will likewise be assumed that the stop bars 242 and 243 have been so adjusted (Figures 3, 13 an'd 22) that the workpiece W will be supported approximately coaxial with the tubular shaft |42 and chucking sleeve |99, and also that their beveled ends 246 and 241 will properly engage iz Y (Figure 2), it shifts the valve vplunger 362 of the valve 36| by reason of its frictional connection (Figure 2l) with the link 364 connected to the valve plunger 362. 'I'his action shifts the valve 36| to admit compressed air from the pipe 359 into the pipe |86, whence it passes into the' annular chamber |69 (Figure 14) and through the passageways |62, I SI and |69 into the righthand end of the cylinder bore |51. The compressed air thus admitted shifts the piston head |88 to the left, carrying with it the sleeve -|99 rigidly connected thereto. The pressure of the coil spring 2|6, however, against the plunger 2I4 maintains the latter in its extreme righthand position with the cross bar 2| I against the annular shoulder 2|!) of the bell-shaped member 263 during the initial part of the left-ward stroke of the sleeve |99.

During the initial left-ward motion of the sleeve |99, while the plunger 2I4 and pivot pin 222 remain temporarily stationary, the coaction of the side walls of the bores 2|9 in the sleeve |99 with the rounded ends 220 of the fingers 22| swings the projecting tips 225 of the fingers 22| into the sleeve |99, as shown in Figure 15. The continued motion of the sleeve |99 to the left, however, pulls the plunger 2|4 and cross bar 2|| to the left into the interior of the bell-shaped member 208, leaving the abutment 299 completely unobstructed. The parts now occupy the positions shown in Figure 16, ready for the arrival of an unground workpiece at the .the workpiece on the chuck and force it against Y the abutment 209 (Figure 14).

In order to start the feeding of a workpiece to the empty chucking sleeve |99, the operator shifts the hand lever 98 to actuate the valve 64 (Figures 1 and 2) and admit compressed air to the pipe 53 at the upper end of the cylinder 48. This causes the piston head 46 and Ipiston rod 45 to move downward, swinging the grinding head housing I8 downward and rearward around .its pivot shaft I6.

grinding position in front of the annular abutment surface 269.

`The grinding head housing I8 continues t0 move downward (Figure 2) until the beveled end 353 of the abutment arm 354 momentarilyrengages the roller 348 on the bell-crank 345 and swings it in a clockwise direction, forcing the valve stem 343 downward and opening the valve 342. This permits compressed air to pass through the valve 342 from the pipe 359 into the pipe 34| and thence into the chamber above lthe diaphragm 322. l'Elie diaphragm 322 iiexes downward, pushing the Valve plunger 3I9 downward. This causes compressed air to pass through the valve 3|6 from the pipes 359 and 3I8 to the pipe 3I3, admitting air beneath the piston 301 and forcing it and the feeding frame 2,63 upward from the position of Figure 9 to that of Figure 13.

As the frame 263 moves upward to the position of Figure 13, the left-hand end of the cross bar 264 engages and lifts the arm 293, raising the plunger 288 against the push of the spring 289 and swinging upward the detent lever 283 and its finger 285. A workpiece W is therefore permitted to roll down the chute 212, but temporarily encounters the gate portion 21| to prevent'it from dropping into the feed frame 263.

Meanwhile, the detent armv 354, having passed by the roller 348, permits the bell-crank 345 to swing upward to its original position under the influence of a coil spring (not shown)l within the valve 342 and engaging and urging the valve stem 343 upward. This action cuts off the further delivery of compressed air from the pipe 359 to the 'pipe 34|. Impelled by the coil-spring 329 (Figure 13), the diaphragm 322 moves slowly upward as the compressed air escapes from the -chamoer 336 through the needle valve 336 and pipe 349 (Figure ll).

This mechanism thus acts as a dash pot to impart a time delay or dwell to the upward motion of the valve plunger 3I9 of the valve 3|'6.

The upward motion of the valve plunger 3| 9 shifts the valve 315 and causes compressed air to be admitted to the pipe 3io (Figure 9), shifting the piston head 3437, piston rod 3B! and slide block 258 downward (Figure 15)). This action moves the feed frame 263 downward from the position of Figure 13 to that of Figure As the feed. frame 253 moves downward, the detent lever 283 and its finger 285 move downward behind the foremost workpiece W (Figure 13), preventing the second and subsequent workpieces from following the first workpiece in the chute 272. The downward motion of the feed .frame 263 also moves the gate 27| downward, permitting the foremost workpiece W to drop from the inclined chute 272 into the vertical chute which in effect is formed between the parallel plates 279 and 278 (Figures 5, 9, 10 and 14). es the chucking sleeve |99. and its fingers 22| are in their retracted positions at this time (Figure 16), the feed frame 2l3 moves downward uninterruptedly until the workpiece W, which has been resting upon the portions 257 and 269 (Figure 12), comes to rest upon the ends 246 and 247 of the stop bars 242 and 253. The beveled ends 246 and 247 tend to urge the workpiece W against the annular abutment surface 263 and support the workpiece against the pressure exerted thereon by the grinding wheel.

Meanwhile, the continued downward motion of the grinding head housing i3 (Figure 2) causes the friction connection 356, Sti to slip ioosely along the slot 365 in the link 35e after the valve plunger 352 has reached its lowest position. When the grinding head housing i8 reaches its lowermost position, the push rod l i5 on the housing i8 (Figure 2) engages the switch plunger ||2 of the limit switch i and closes the circuit through this normally open switch. During the same period, the downward motion of the feed frame 263 has caused the slide block 253 to engage and push downward the rounded end of the contact arm 295, rotating the rod 2% (Figure 5) and swinging the arm 293 to push the operating plunger |25 of the limit switch |8 upward, closing the circuit through this switch. .As the limit switches lil and H8 are in series with one another, the solenoid lill becomes energized from the electric wires 85 and 82, assuming of course that the manual switch Sii is closed (Figure 1).

The energization of the solenoid i it causes its armature |09 to be shifted upward, its top if??? engaging and shifting the bell crank lever |25 (Figure 19) to the left around its pivot iil. This swings the arm 99, shaft 73 and arm 72 .in a counterclockwise direction, shifting the valve plunger 58 of the valve $4 inward. This action reverses. the flow of pressure uid to the 4cylinder 48, causing it to enter by the pipe 5t heneath the piston head 4S. The pressure fluid causes the piston rod 45 to move upward, swinging the grinding head l@ upward and causing the grinding wheel 26 to be swung into contact with the workpiece W.

While this is occurring, the upward motion of the grinding head housing i8 through its frictional connection 356, 367 (Figure 2l) with the link 354 lifts the latter and with it, the valve plunger 382 (Figure 2), shifting the chuckinff control valve 36|. .Compressed air now passes from the pipes 339 and 320 into the pipe HV (Figure 10), thence into the chamber |75 (Figure 14) from which it proceeds through the passageway |67 into the left-hand end of the cylinder bore |57. This causes the piston head 588 and piston rods and |34 to move to the right, projecting the chucking sleeve |99 through the bore 2| 5 (Figure l5) and likewise through the bore in the workpiece W.

When the cross bar 2|| reaches the annular shoulder 2|@ within the bell-shaped member 208,. it and the plunger 213 come to a halt. Since the piston rod |34 and sleeve |59 are still moving to the right (Figures 15 and 16), the engagement of the walls of the holes 2li? with the rounded ends 223 of the fingers 22| causes these to swing in a counterclockwise direction, bringing their ends 225 into engagement with the end of the workpiece W and forcing it against the annular abutment surface 209 while the coil spring 235 is being compressed. The workpiece W is now clamped in position against the annular abutment surface 2139, and slides on this surface while remaining in contact with the stop bars 2&2 and 243.

The rotation of the tubular shaft |42 by the electric motor |5| (Figure l) through the gear train. |52, |45 and |45 causes the sleeve |99 and workpiece W to be rotated while the grinding wheel 2 is swung into contact with it. As the grinding wheel 2li engages the workpiece Vv', the timing device 87 operates to regulate the duration of the grinding period. When the timing device (i7 shifts the switch member 8B so that the contact engages the contact S, the er1- ergization circuit of the solenoid 78 is thereby closed. This causes the armature 77 to be drawn into the solenoid 78, swinging the arm 72, shaft 73 and arm 99 clockwise, and pulling the valve plunger 68 outward away from the valve 64. This action again reverses the ow of pressure fluid to the grinding head cylinder t8 at the instant the parts are in the positions shown in Figures 1, 2, 3, 9 and 10.

By the reversal of the valve 64 just described, pressure duid is admitted to the pipe 53 at the upper end of the cylinder 48, urging the piston head 15, piston rod @5 and grinding head housing I8 downward around the pivot shaft It. The foregoing cycle of operations is then repeated as described above, except that the operator no longer needs to touch the handlever 9B to actuate the valve et. Furthermore, since there is a workpiece on the sleeve |92, the retraction thereof with. its fingers 22| from the position of Figure 14 to the position of Figure 16 leaves the ground workpiece W resting upon the ends of the stop bars 252 and 243 with the feed frame members 257, 26S and 27!) beneath the workpiece W in the position shown in Figure 3. The subsequent upward motion of the feed frame 263 lifts the ground workpiece W upward until it reaches the chute 273 in the position shown in Figure 13, whereupon the ground workpiece W is dumped upon the chute 273 and rolls downward along it into a suitable receptacle. The -foregoing operations then repeat themselves automatically as long as the workpieoes W are supplied to the chute 2l? and as long as the machine is supplied with pressed air and electricity.

What I claim is:

l. A workpiece holding apparatus fol-fa centerless grinding machine, comprising, a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having an opening therethrough anda workpiece abutment portion disposed adjacent Said opening, and a workpiece clamping structure rotatably mounted on said support coaxial with pressure fluid, comsaid abutment and having workpiece clamping mechanism retractible into said openingwholly inwardly of said abutment' portion andA movable axially outwardly through said opening, said mechanism including a workpiece clamping member pivotally mounted thereon and responsive to the axial outward motion thereof to swing outwardly and axially into clamping engagement with the end of the workpiece and urging the workpiece axially against said abutment portion.

2. A lworkpiece feeding and holding apparatus for a oenterless grinding machine, comprising a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having an opening therethrough and a workpiece abutment portion disposed adjacent said opening, a tubular element rotatably mounted on said support coaxial with said abutment and movable axially outwardly relatively thereto through said opening, a plunger mounted within said tubular element and reciprocable relatively thereto, and workpiece clamping mechanism retraotble into said opening wholly rearwardly of said abutment portion, said mechanism including a workpiece clamping member pivotally mounted on said plunger, said clamping member having one end engageable with said tubular element and responsive to the relative reciprocation between said tubular element and said plunger for swinging the other end of said clamping member outwardly and axially into clamping engagement with the end of the workpiece and urging said workpiece axially against said abutment portion.

3. A workpiece feeding and holding apparatus for a oenterless grinding machine, comprising a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having `an opening therethrough and a workpiece abutment portion disposed adjacent said opening, a tubular element rotatably mounted on said support coaxial with said abutment and movable outwardly relatively thereto through said opening, a plunger mounted within said tubular element and reciprocable relatively thereto, and workpiece clamping mechanism retractible into said opening lwholly rearwardly of said abutment portion, said mechanism including a workpiece clamping member pivotally mounted on said plunger, said clamping member having one end engageable with said tubular elements and responsive to the axial motion thereof of Said plunger for swinging the other end of said clamping member outwardly and axially into clamping engagement with the end of the workpiece and urging said workpiece axially against said abutment portion.

4. A workpiece feeding and holding apparatus for a oenterless grinding machine, comprising a support mounted on said machine, a rotary w-orkpiece abutment rotatably mounted on said support and having an opening therethrough and a workpiece abutment portion disposed adjacent said opening, a workpiece clamping structure rotatably mounted on said support coaxial with said abutment and having workpiece clamping mechanism retractible into said opening wholly inwardly of said abutment portion and movable axially outwardly through said opening, said mechanism including a workpiece clamping member pivotally mounted thereon and swingable outwardly and axially into clamping engagement with the end of the workpiece to urge the workpiece axially against said abutment portion, and

lworkpiece feeding mechanism operable in timed Y relationship with the reciprooation of said clampof said clamping structure relatively to said abutment portion.

5. A workpiece feeding and holding apparatus for a oenterless grinding machine7 comprising a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having an opening therethrough and a workpiece abutment portion disposed adjacent said opening, `and a workpiece clamping structure rotatably mounted on said support coaxial with said abutment and having workpiece clamping mechanism retractible into said opening wholly inwardly of said abutment portion and movable axially outwardly through said opening, said mechanism including a plurality of oppositely directed workpiece clamping members pivotally mounted thereon and lwith their opposite ends swingable outwardly and .axially into clamping engagement with the end of the workpiece to urge the workpiece axially against said abutment portion.

6. A workpiece feeding and holding apparatus for .a oenterless grinding machine, comprising a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having an opening therethrough and a workpiece abutment portion disposed `adjacent said opening, a workpiece clamping structure rotatably mounted on said support coaxial with said abutment and having workpiece clamping mechanism retractible into said opening wholly inwardly of said abutment portion and movable axially outwardly through said opening, said mechanism including a workpiece clamping member mounted thereon and extensible outwardly into clamping engagement with the workpiece against said abutment portion, a Iworkpiece supply carrier, a vertically 'reciprocable workpiece feeder disposed adjacent said carrier in workpiece-receiving relationship therewith and movable between said carrier and said lworkpiece abutment portion, and mechanism operable in timed relationship with the motion of said clamping structure to feed an unground workpiece from said supply carrier to a position adjacent said abutment portion. I

7. A workpiece feeding and holding kapparatus for a oenterless grinding machine, comprising a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having an opening therethrough, a workpiece clamping structure rotatably mounted on said supportv coaxial with said abutment and having a portion thereof movable axially through said opening, said structure including a workpiece clamping member mounted thereon and extensible outwardly into clamping engagement with the workpiece against said abutment, a Iworkpiece supply carrier, a workpiece discharge carrier, a vertically reciprocable workpiece feeder disposed adjacent said carriers in workpiece receiving and discharging relationship therewith, said feeder being movable between said carriers and said workpiece abutment, and mechanism operable in timed relationship with the motion of said clamping structure alternately to convey af ground workpiece from said abutment to lsaid 'discharge carrier and to convey an unground workpiece from said supply carrier to a position adjacent said abutment.

8. A workpiece feeding and holding apparatus for a oenterless grinding machine, comprising a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having an opening therethrough, a workpiece clamping structure rotatably mounted on said support coaxial iwith said abutment and having a portion thereof movable axially through said opening, said structure including a workpiece clamping member mounted thereon and extensible outwardly into clamping engagement with the workpiece against said abutment, a workpiece rest disposed adjacent said abutment in workpiece-aligning relationship therewith, a workpiece supply carrier, a vertically reciprocable workpiece feeder disposed adjacent said carrier in workpiece-receiving relationship therewith and movable between said carrier and said workpiece abutment, and mechanism operable in timed relationship with the motion of said clamping structure to feed an unground workpiece from said supply carrier to said rest adjacent said abutment.

9. A workpiece feeding and holding apparatus for a centerless grinding machine, comprising a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having an opening therethrough, a workpiece clamping structure rotatably mounted on said support coaxial with said abutment and having a portion thereof movable axially through said opening, said structure including a workpiece clamping member mounted thereon and extensible outwardly into clamping engagement with the workpiece against said abutment, a workpiece rest disposed adjacent said abutment in workpiece-aligning relationship therewith, a workpiece supply carrier, a workpiece discharge carrier, a vertically reciprocable workpiece feeder disposed adjacent said carriers in workpiece receiving and discharging relationship therewith, said feeder being movable between said carriers and said workpiece abutment, and mechanism operable in timed relationship with the motion of said clamping structure alternately to convey a ground workpiece from said rest to said discharge carrier and to convey an unground workpiece from said supply carrier to said rest adjacent said abutment.

10. A workpiece feeding and holding apparatus for a centerless grinding machine, comprising a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having an opening therethrough and a workpiece abutment portion disposed adjacent said opening, a workpiece clamping structure rotatably mounted on said support coaxial with said abutment and having workpiece clamping mechanism retractible into said opening wholly inwardly of said abutment portion and movable axially outwardly through said opening, said mechanism including a Iworkpiece clamping member mounted thereon and extensible outwardly into clamping engagement with the workpiece against said abutment portion, a workpiece supply carrier, a vertically reciprocable workpiece feeder disposed adjacent said carrier in workpiece-receiving relationship therewith and movable between said carrier and said workpiece abutment portion, a movable workpiece detent positioned adjacent the outlet of said supply carrier and movable into and out of workpiece detaining relationship therewith, and mechanism operable in timed relationship with the motion of said clamping structure to move said detent out of its workpiece-detaining position and feed an unground workpiece from said supply carrier to a position adjacent said abutment portion.

11. A workpiece feeding and holding apparatus for a centerless grinding machine, comprising a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having an opening therethrough, a workpiece clamping structure rotatably mounted on said support coaxial with said abutment and having a portion thereof movable axially through said opening, said structure including a workpiece clamping member mounted thereon and extensible outwardly into clamping engagement with the workpiece against said abutment, a workpiece supply carrier, a workpiece discharge carrier, a vertically reciprocable workpiece feeder disposed adjacent said carriers in workpiece receiving and discharginfr relationship therewith, said feeder being movable between said carriers and said workpiece abutment, a movable workpiece detent positioned adjacent the outlet of said supply carrier and movable into and out of workpiece detaining relationship therewith, and mechanism operable in timed relationship with the motion of said clamping structure to move said detent out of its workpiece-detaining position and alternately to convey a ground workpiece from said supply carrier to a position adjacent said abutment.

l2. A workpiece feeding and holding apparatus for a centerless grinding machine, comprising a support mounted on said machine, a rotary workpiece abutment rotatably mounted on said support and having' an opening therethrough, a workpiece clamping structure rotatably mounted on said support coaxial with said abutment and having a portion thereof movable axially through said opening, said structure including a workpiece clamping member mounted thereon and extensible outwardly into clamping engagement with the workpiece against said abutment, a workpiece supply carrier, `a workpiece discharge carrier, a vertically reciprocable workpiece feeder disposed adjacent said carriers in workpiece receiving and discharging relationship therewith, said feeder being movable between said carriers and said workpiece abutment, a movable workpiece detent positioned adjacent the outlet of said supply carrier and movable into and out of workpiece detaining relationship therewith, mechanism operable in timed relationship with the motion of said clamping structure to move said detent out of its workpiece-detaining position and alternately to convey a ground workpiece from said supply carrier to a position adjacent said abutment, and a time delay device responsive to the upward motion of said feeder from said `abutment to said discharge carrier into a predetermined raised position thereof to hold said feeder a predetermined time period in said raised position thereof.

GLEN F. JOHNSON.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,816,170 Booth 1 July 28, 1931 1,947,957 Lillman Feb. 20, 1934 2,040,449 Stevens May 12, 1936 2,260,843 Strong Oct. 28, 1941 2,380,761 Hutchinson July 31, 1945 

